我想从动态列表中选择列表字段名称为例如' SecName'并且SecName值等于例如' xxx', 我知道如何在sql中创建它,但我想创建并使用它与实体框架。 就像在sql中执行String一样。 我怎样才能在实体框架和linq中实现它。 它应该是这样的
var lst=_efmodel.Tables.where(x=>x.fieldname=="SecName" && x.value=="xxx").tolist();
我正在寻找通过传递两个字符串来过滤我的列表的语法,第一个字符串应该是属性Name而另一个应该是该属性值。
答案 0 :(得分:2)
搜索后我找到了答案,答案是:
public class SearchField
{
public string Name { get; set; }
public string @Value { get; set; }
//public string Operator { get; set; }
public SearchField(string Name, string @Value)
{
this.Name = Name;
this.@Value = @Value;
//Operator = "=";
}
}
public class FilterLinq<T>
{
public static Expression<Func<T, Boolean>> GetWherePredicate(params SearchField[] SearchFieldList)
{
//the 'IN' parameter for expression ie T=> condition
ParameterExpression pe = Expression.Parameter(typeof(T), typeof(T).Name);
//combine them with and 1=1 Like no expression
Expression combined = null;
if (SearchFieldList != null)
{
foreach (var fieldItem in SearchFieldList)
{
//Expression for accessing Fields name property
Expression columnNameProperty = Expression.Property(pe, fieldItem.Name);
//the name constant to match
Expression columnValue = Expression.Constant(fieldItem.Value);
//the first expression: PatientantLastName = ?
Expression e1 = Expression.Equal(columnNameProperty, columnValue);
if (combined == null)
{
combined = e1;
}
else
{
combined = Expression.And(combined, e1);
}
}
}
//create and return the predicate
if (combined != null) return Expression.Lambda<Func<T, Boolean>>(combined, pe);
return null;
}
}
并像这样使用它:
var lst = _efmodel.Count(2015).AsQueryable()
.Where(
FilterLinq<PazTedad_Result>.GetWherePredicate(
new SearchField("FieldName", "FieldValue"))).ToList();
答案 1 :(得分:0)
代码必须是这样的吗?
var lst=_efmodel.Table.Where(x => x.fieldname == <SomeValue>).ToList();